Method of producing an iron alloy



Patented Dec. 13, 1938 UNITED STATES PATENT OFFICE 2,139,939 IHETHOD OFPRODUCING AN IRON ALLOY of New York No Drawing. Application May 15, 1936Serial No. 79,922

3Claims.

This invention relates to the production of a cast-iron alloy of suchnature that when used to form objects that are subjected to frequent andconsiderable heat such objects will not substan- 5 tially andpermanently increase in size, change in shape or undergo undue crackingfrom repeated heating. An illustration of some of such objects are thoseparts of a cast-iron warmair furnace, stove or the like, that aresubjected to the i0 direct and repeated actions of the heat such as thefirepots, fire domes, grates and the like. These examples are to beunderstood as illustrative only and not as limiting the scope of ourinvention, as many other illustrations might be cited as being equallyapplicable.

' It has been the history of cast-iron warm air furnaces and stoves,that certain parts will frequently crack or burn out when operatingunder certain unfavorable conditions such as over-firing of the furnace,the use of certain types of coal, insuflicient air supply to the-heater,and other conditions. The need has long been felt of being able todevelop some kind of cast-iron which would have properties that wouldmore greatly resist and these conditions.

Upon high heating, prior to the present invention, the castingssubjected to the direct and repeated actions of the heat would expand,and when allowed to cool would contract This repeated expansion andcontraction has a wearing and tearing action upon the fibre of thecastiron. Under each reheating they would expand more and more and nevereventually return to their original or true dimensions. .They would 5generally warp out of shape irregularly and unevenly. In doing this theywould frequently carry this warpage into adjoining castings which arefitted to them. Damage is thus also done to other castings which are notunder the same ,0 stress of high temperature and which ordinarily wouldnot expand out of shape to such a great extent.

For the purposes of this specification we term this failure of suchcastings to return, after repeated expansions, to their original or truedimensions, as growt In other words, they eventually grow or increase insize, and sufier'an undue permanent deformation. This "growth continueswith repeated expansions, with its destructive action, until the verybody of the castiron begins to tear apart and cracks appear in thecastings.

After these cracks are once started, deteriorating elements in thecombustion of the fuel are able to penetrate intr these cracks and helpadd to the destructive action. taking place. These cracks eventuallyenlarge to such an extent that finally a direct break will occur and ahole be gradually burned through the casting.

After careful investigations and study we have found that when chromiumis introduced into cast-iron, it refines the grain of the casting,delays the breaking up of that constituent, or those constituents, whichpromote the general tensile strength of gray iron castings, and stops orsubstantially stops growth and cracking in the casting.

In our experiments and developments we have discovered that the abovementioned defects and disadvantages can be substantially eliminated byadding to the molten cast-iron from 1 to 1.5 percent of chromium, themolten cast-iron being raised, prior to the addition of the chromium, toa temperature somewhat higher than that used in customary gray ironpractice, and the molten iron, after the addition of the chromium, beingmore quickly transferred to the mold and poured immediately to avoidundue cooling of the iron.

Among the objects of our invention are the overcoming of thedisadvantages and the gaining of the advantages pointed out above.

A further object is the prevention of substantial growth in cast-ironparts subjected to considerable and frequent heating.

Another object is the prevention of substantial cracking in cast-ironparts subjected to considerable and frequent heating.

A still further object is the provision of novel steps in handling thecast-iron in melting it and adding chromium thereto in properproportions.

A further object is the addition of the chromium to the molten cast-ironat the proper time and place, the heating of the iron to a highertemperature, and the quick handling of the molten iron after thechromium is added.

Another object is the production of a new iron alloy for the purposesstated.

Other objects, advantages and capabilities inherent in our inventionwill later more fully appear.

The growth or permanent substantial deformation of the usual cast-ironparts subjected to considerable heat causes considerable difiiculty whenit is necessary to replace an old permanently deformed part with a newpart that is required to correctly interfit with another part that islikewise permanently deformed. The new part in suchinstances does notproperly interfit with the old part because of the new part having thecorrect original dimensions while the original di- An instance of thisis found in cast-iron warm air furnaces and stoves which have been inuse for some time and in which it is found necessary to replace one ofthe parts, such as in the firepot, fire dome, .grates, etc., these beingthe parts subjected to the most heat and consequent deformation. Whensuch new part does not interfit with the cooperating old part it isgenerally necessary to have to also order another new part to take theplace of the old part, thus involving additional delay as well asfurther expense.

By our present invention this delay and additional expense is avoided,thus affording the purchasing public the advantageof economy as well assaving in time. Many other instances than the specific parts of heatingfurnaces and stoves mentioned above could be cited, but these serve aspassing illustrations of the value to the general public of the presentinvention. With cast-iron parts made in accordance with the presentinvention such repairs or replacement will be necessary much lessfrequently, and even should they, in greater length of time, be neededthe expense and delay would be very much less.

In the production of the alloy of the present invention we add chromiumto the molten castiron, either in the cupola or preferably as it runsfrom the cupola orbther melting device, in an amount approximatelybetween 1 to 2 percent. Among the compositions or mixtures of thecastiron to which we have found it especially advantageous' to add thechromium, and preferably from 1 to 1.50 percent, is:

Carbon 3.00 to 4.00 percent Silicon 2.25 to 2.75 percent Sulphur .05percent and under Phosphorous .50 to .80 percent Manganese .50 to 1.00percent the balance being approximately pure iron. Materials of otherand varying contents may be similarly treated to advantage with asimilar content of chromium. Where we add the chromium to the moltenmetal in the cupola, we prefer to have the chromium in the form ofbriquettes.

The chromium we preferably obtain'in the form of what is commerciallycalled ferro chrome, which contains from to percent chromium,

3 to 4 percent silicon and 4 to 5 percent carbon.

Carbon 3.00 to 4.00 percent Silicon; 2.25 to 2.75 percent Sulphur .05percent and under, Phosphorous .50 to .80 percent Manganese .50 to 1.00percent Chromium"; 1.00 to 2.00 percent Pure iron 92.70 to 89.45 percentIn the carrying out of our improved method for the production of our newalloy, the castiron, which is preferably a mixture of scrap and pigiron, is melted in a cupola or the like to a temperature somewhat higherthan that employed in the usual gray iron practice. The

chromium is preferably added after the molten iron emerges from the taphole in the breast of the cupola, the addition of the chromium occurringintermediate the tap hole and the receiving ladle. In our particularpractice the molten iron flows from the tap hole down an inclined.stationary spout and into a tiltable spout that can be tilted to eitherside in order to conduct the flowing stream of molten iron into areceiving ladle on either side of the front of the cupola.

We have found it good practice to introduce the chromium into theflowing stream of molten iron at the point where the stream passes fromthe stationary spout of the cupola into the tilting spout for conductingit to the ladle. The chromium may be in the form known commercially asferro chrome. The desired amount of this ferro chrome may be placed in acontainer positioned just above the point of delivery of chromium to themolten iron, which container may be open at the top and provided on itsbottom with a downwardly extending spout of such size in cross-sectionas to deliver the ferro chrome into the molten stream of iron at suchspeed that the period of flow of the desired amount of chromium will befrom the time that about the first fifty pounds of molten iron isaccumulated in say, for example, a one thousand pound ladle, up toshortly before the ladle is filled to its intended capacity. Just theintended amount for the size of the ladle being used may be dumped intothe container so that within the time just enumerated this amount willflow through the spout of the container and the container be emptied atthe desired time prior to the filling of the ladle; or, if desired, agreater amount of the ferro chrome may be placed in a container having aspout that will give a certain rate of flow, and

the opening of the spout be opened and closed at the desired times, theamount of chromium added,

being determined by the length of the time of fiow.

Assuming the receiving ladle to hold one thousand pounds of molten iron,about fifty pounds of molten iron may be run into the bottom of theladle and the stream of ferro chrome then started and continued, aspointed out, up to shortly before the ladle is filled to its intendedcapacity,

when the stream of chromium will either have stopped of its own accordif the container holds only the desired amount for one ladle full ofiron, or the stream will be cut off at that time shortly before theladle is filled to its intended capacity if the amount of chromium isbeing regulated by rate of flow. As the percentage of chromium in pounds(11.55 lbs.) of chromium to one thousand pounds of molten iron or, inother words, would add from approximately 1 to 2 percent of chromium tothe iron. This exact proportion may be somewhat varied but we find it tobe satisfactory when the percentage of chromium runs some-- wherebetween 1 to 2 percent.

While we have stated the exact point of the flowing stream of molteniron at which we prefer to add the chromium, this point may be variedwithin reasonable limits. The chromium will be partially mixed with thestream of molten iron as it flows along the spout and into the ladle,

which mixing will be completed inthe ladle by the ebullition or boilingaction of the molten iron is filled to its intended capacity, andtransportwithin the ladle.

As soon as the ladle is filled to its intended capacity with the mixtureof molten iron and chromium, the transporting of the ladle to the moldor to such other ladle as the molten iron may be transferred to, and thepouring of the mold, is to be accomplished in a shorter time than isusual in the customary gray iron practice, as the addition of thechromium to the molten iron creates a tendency for it to solidifyquicker than would such iron without chromium being added thereto. L

No mechanical mixing is necessary as the action of the flowing stream ofmolten iron, together with the boiling action of the molten iron in theladle, is sufiicient to thoroughly mix the chromium with the molteniron. 4 I

Some of the articles made from the iron alloyand by the method disclosedherein are set forth and claimed in the copending application of WilliamJ. Doyle, Serial No. 41,283, 'flled September While the percentages ofingredients of the iron alloy given above may be varied, the limitsstated herein are considered as giving satisfactory results.

Having now described our invention, we

claim:

1. The method of producing an iron alloy that will not suffer unduepermanent growth or crack ing from high heating, which consists inmelting ing the molten iron to and pouring it into a mold more quicklythan is customary in gray iron practice.

2. That step in the method of producing a cast-iron alloy that will notsufier undue perma nent growth or cracking from heating, which consistsin adding from 1 to 1.50 percent of chromium'to the flowing stream ofmolten iron as it flows from a cupola or the like, the chromium beinggranular and added in a flowing stream to the flowing stream of molteniron at a point intermediate the ladle and the cupola tap hole.

3. The method of producing an iron alloy that will not sufier ,unduesubstantial growth, deformation or cracking from heating, which consistsin melting cast-iron in a cupola, or the like, at a temperature higherthan that used in customary gray iron practice, measuring out suchquantity of ferro chrome in granular form of approximately percentchromium content that will add from between 1 to 2 percent of chromiumto the molten iron when the ladle is filled to its intended capacity,placing said ferro chrome in a container having a spout and supportedalcovev the cupola spout between the tap hole and the ladle, flowing themolten iron in astream from the cupola to a ladle until a small amountof molten iron is accumulated in the ladle, then causing the granularferro chrome to flow in a pacity, and transporting the molten iron toand pouring it into a mold more quickly than is customary in gray ironpractice.

1!]; '1 J. DOYLE. JUS'I'US J. 3:

